Preparation method and application of curved-surface flaky terahertz wave absorbing agent

Abstract

The invention belongs to the field of terahertz wave-absorbing materials and device integration thereof, and particularly provides a preparation method and application of a curved-surface flaky terahertz wave-absorbing agent, which are used for solving the problems that the bandwidth of the existing wave-absorbing material is insufficient, the integration of the wave-absorbing material, a coupler and a matched load is complicated, and the like. According to the invention, a polystyrene sphere (PS) sphere template is utilized, a graphene nanosheet (GNS) material with electromagnetic loss capability is adopted as a raw material of the wave-absorbing agent, and after full condensation reaction with a silane coupling agent, the material can be adsorbed on the surface of the PS sphere in a conformal manner, so that a curved sheet structure is presented on the spatial scale. The wave-absorbing agent with the curved surface structure is obtained through self-assembly on the premise that material components are not changed without doping or dipping other wave-absorbing agents with loss capacity, and the broadband strong absorption performance is achieved by utilizing the multiple reflection principle of the curved surface structure; in addition, integration of the wave-absorbing material and the coupler is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of terahertz wave-absorbing materials and device integration, and specifically provides a preparation method of a curved sheet-shaped broadband wave-absorbing agent and its application in a coupler. BACKGROUND

[0002] With the rapid development of millimeter wave and terahertz technology, the demand for high-performance wave-absorbing materials is increasing, which shows great application value in electromagnetic shielding, wireless communication, security imaging, radar detection, atmospheric remote sensing and astronomical exploration, etc. At present, the mainstream wave-absorbing agents mostly adopt a planar multilayer structure or a uniform composite material, which can achieve electromagnetic wave absorption in some frequency bands through impedance matching, but the adaptability to oblique incidence or wideband signals is poor, and it is difficult to suppress energy leakage caused by multiple reflections. In addition, the integration of conventional wave-absorbing bodies and functional devices (such as couplers and waveguides) often faces the problem of interface mismatch, which leads to a decrease in the overall efficiency of the device and limits the practical process of terahertz technology.

[0003] In recent years, design strategies based on macroscopic and microscopic structures have been introduced into the field of terahertz wave-absorbing, which significantly improves the wave-absorbing bandwidth and efficiency by regulating the propagation path and local field distribution of electromagnetic waves. For example, metasurfaces can enhance loss through resonance effects, but such designs require very high processing precision, and complex structures can easily cause consistency problems in preparation. At the same time, to meet the needs of device integration, some studies have attempted to embed wave-absorbing units into waveguides or antenna arrays, but planar wave-absorbing bodies cannot fully utilize the internal space of the device, resulting in limited wave-absorbing path, which can suppress some reflected noise, but cannot adapt to the propagation characteristics of electromagnetic waves in the device (such as field strength gradient distribution and multi-modal coupling effect), making it difficult to further improve the wave-absorbing efficiency and directivity. Therefore, there is an urgent need for a new type of structure wave-absorbing agent and its integration method with devices, which can realize wideband and high-efficiency absorption in a limited space through deep coupling of microscopic geometric morphology and electromagnetic characteristics, and meet the high absorption performance and miniaturization application requirements of terahertz devices. SUMMARY

[0004] The present application aims to provide a preparation method of a curved structure wave-absorbing agent and its integrated application in a coupler with a center frequency of 140 GHz, to solve the problems of insufficient bandwidth of existing wave-absorbing materials and complex integration of wave-absorbing materials with couplers and matching loads. The present application uses polystyrene ball (PS) templates and adopts a self-assembly template method without the need for doping or impregnating other lossy wave-absorbing agents. The curved structure wave-absorbing agent is self-assembled without changing the material composition, and the wideband strong absorption performance is realized by using the principle of multiple reflections of the curved structure. Moreover, the integration of the wave-absorbing material and the coupler is realized.

[0005] To achieve the above-mentioned purposes, the technical scheme adopted by the present application is:

[0006] A method for preparing a curved sheet-like terahertz absorbing agent, characterized by comprising the following steps:

[0007] Step 1. Preparation of graphene nanosheet solution: Dissolve graphene nanosheet (GNS) raw material in 50ml~100ml deionized water, add graphene dispersant, and stir with a magnetic stirrer at 500~700rpm for 20~40min to obtain a uniformly dispersed GNS aqueous solution.

[0008] Step 2. Sheet / sphere material linking: According to the mass ratio of GNS to polystyrene spheres (PS) of (0.1~2):1, PS microspheres are added to GNS aqueous solution. Silane coupling agent is used to modify the surface of GNS. The organic functional groups of silane coupling agent combine with PS microspheres, and at the same time, the silanol ends form covalent bonds with the surface of GNS, so that GNS and PS spheres are tightly linked.

[0009] Step 3. Shaping and drying: Freeze the above-obtained solution at -18℃ to -20℃ for 8h to 10h to form a solid, and freeze-dry for 24h to 30h to obtain a flocculent block. Grind the block to obtain a powder with good flowability, which is the curved sheet terahertz absorbing agent.

[0010] Furthermore, in step 1, the dispersant accounts for 1.0–1.5 wt% of the graphene nanosheet raw material.

[0011] Furthermore, in step 2, the silane coupling agent is added at a mass percentage of 1.0–1.5 wt% of the tablet / sphere solution, and the mixing time after adding the silane coupling agent is 15 min.

[0012] Furthermore, in step 2, the diameter of the polystyrene spheres (PS) is 3 μm to 10 μm.

[0013] The application of a curved sheet-like terahertz absorbing agent in a coupler is characterized by dispersing the curved sheet-like terahertz absorbing agent in epoxy resin, and obtaining an absorbing slurry after defoaming treatment; conformally filling the absorbing slurry into the isolation end of the coupler, and obtaining an absorber of the corresponding shape after curing the absorbing slurry, thereby realizing the conformal integration of the absorber and the isolation end of the coupler.

[0014] Furthermore, the curved sheet terahertz absorbing agent accounts for 5 wt% to 20 wt% of the total mass (curved sheet terahertz absorbing agent and epoxy resin).

[0015] In terms of working principle:

[0016] Graphene nanosheets offer advantages such as lightweight and designability due to their large specific surface area; while polystyrene spheres (PS) are non-conductive, and their spherical structure can serve as a good conformal template. Therefore, this invention uses PS as a template and employs a self-assembly template method to prepare curved sheet-like microwave absorbers. Unlike other simple planar sheet-like microwave absorbers, curved sheet-like microwave absorbers can effectively absorb electromagnetic waves by subjecting incident electromagnetic waves to multiple reflections and scattering, increasing the propagation path and reducing multiple losses, thus achieving broadband strong absorption performance.

[0017] In summary, the beneficial effects of the present invention are as follows:

[0018] This invention proposes a curved sheet-like absorbing agent. The curved sheet-like absorbing agent is synthesized without doping or impregnating with other absorbing agents or altering the material composition. The curved structure significantly increases the propagation path of terahertz waves, and due to multiple reflections, the incident electromagnetic waves gradually weaken, effectively absorbing and reducing electromagnetic waves—a terahertz absorbing effect achieved through multiple reflections / scattering. Furthermore, this invention enables conformal integration of the curved sheet-like absorbing agent with a coupler, offering advantages such as flexible design, excellent absorption performance, and good controllability. Attached Figure Description

[0019] Figure 1 This is a SEM image of the curved sheet-like terahertz absorbing agent in Embodiment 1 of the present invention.

[0020] Figure 2 This is a diagram illustrating the absorption mechanism of the curved sheet-like terahertz absorbing agent in Embodiment 1 of the present invention.

[0021] Figure 3 This is a diagram showing the absorption performance of the curved sheet-like terahertz absorbing agent in Embodiment 1 of the present invention.

[0022] Figure 4 This is a simulation model diagram of the coupler in Embodiment 2 of the present invention.

[0023] Figure 5 This is a performance diagram of the coupler in Embodiment 2 of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0025] Example 1

[0026] This embodiment provides a method for preparing a curved sheet-like terahertz absorbing agent. Polystyrene spheres (PS) are used as templates, and a self-assembly template method is employed. The PS spheres, as non-polar polymer materials, have dielectric losses close to zero and cannot absorb electromagnetic waves through polarization or loss. Their role in the system is as template material for self-assembly. Based on this, graphene nanosheets with electromagnetic loss capability are used as raw materials for the absorbing agent. After a full condensation reaction with a silane coupling agent, they can conformally adsorb onto the surface of the PS spheres, thereby presenting a curved sheet-like structure on a spatial scale.

[0027] The preparation method of the curved sheet-like terahertz absorbing agent specifically includes the following steps:

[0028] Step 1. Preparation of graphene nanosheet solution: Dissolve graphene nanosheet raw material (GNS) in 50-100 ml of deionized water, add graphene dispersant, and stir at 600 rpm for 30 min using a magnetic stirrer to obtain a uniformly dispersed aqueous solution of GNS.

[0029] Step 2. Sheet / Ball Material Linking: Add polystyrene (PS) balls to the aqueous solution of GNS according to the following ratios: GNS sheet to PS ball mass ratio is 0.1:1, 0.5:1, 1:1, 1.5:1, 2:1, and the diameter of the PS balls is 3μm to 10μm. Add silane coupling agent and mix thoroughly for 15 minutes. The silane coupling agent accounts for 1.0wt% to 1.5wt% of the sheet / ball solution (aqueous solution of GNS and PS balls). The silanol after hydrolysis of the coupling agent condenses with the oxygen-containing functional groups of graphene to provide a stable bond, while the organic end of the silane can form covalent bonds with the ionic bonds of the PS balls, thereby enhancing the interfacial adhesion strength between GNS and PS balls.

[0030] Step 3. Shaping and drying: Freeze the solution at -18℃ to -20℃ for 8 to 10 hours to form the graphene nanosheets, and freeze-dry for 24 to 30 hours to stabilize the graphene nanosheets on the surface of the PS spheres, forming a curved sheet structure. Finally, after grinding, a uniformly dispersed powder is obtained, which is the curved sheet terahertz absorbing agent.

[0031] Taking a mass ratio of GNS:PS = 0.1:1 as an example, such as Figure 1 The image shows the SEM image of the curved sheet-like terahertz absorber prepared in this embodiment. The left image shows the planar nanosheets, and the right image shows the curved nanosheets. As can be seen from the image, this invention uses polystyrene spheres (PS) as templates and successfully conformally adsorbs graphene nanosheets onto the surface of PS spheres through a self-assembly template method to form a curved sheet-like structure.

[0032] Furthermore, such as Figure 2The figure shows the absorption mechanism of the curved sheet terahertz absorber prepared in this embodiment. As can be seen from the figure, compared with planar graphite nanosheets, terahertz waves can be reflected multiple times on curved graphite nanosheets, thereby increasing the loss and absorption of incident terahertz waves.

[0033] like Figure 3 The figure shows the absorption performance test results of the curved sheet terahertz absorber prepared in this embodiment. As can be seen from the figure, the absorption rate of the curved graphite nanosheets all exceeds 87%. At the frequency point of 0.2THz, the absorption rate is 15% higher than that of the planar graphite nanosheets. The reflection loss RL of the curved graphite nanosheets is as wide as 0.8THz with a frequency band of -10dB. The curved graphene nanosheets have high frequency, wide bandwidth and good terahertz absorption performance.

[0034] Example 2

[0035] Based on the curved sheet-like terahertz absorbing agent prepared in Example 1, this example provides the application of the curved sheet-like terahertz absorbing agent in a coupler. The center frequency of the coupler is 140 GHz. The simulation of the coupler is performed using CST software, and its simulation model is as follows: Figure 4 As shown, the electromagnetic parameters of the curved sheet-like terahertz absorbing agent were obtained by time-domain spectrometry.

[0036] The application of the curved sheet terahertz absorbing agent in the coupler is as follows: the curved sheet terahertz absorbing agent is dispersed in epoxy resin at a percentage of 10wt% of the total mass. After defoaming treatment, a flowable absorbing slurry is obtained. The absorbing slurry is conformally filled into the isolation end of the coupler. After the absorbing slurry is cured, an absorber of the corresponding shape is obtained, realizing the conformal integration of the absorber and the isolation end of the coupler.

[0037] The electromagnetic parameters of the absorbing material were obtained using a time-domain spectrometer. These parameters were then substituted into the simulation model of the coupler, and the dimensions of the absorber were optimized by parameter sweeping. Ultimately, a return loss S11 ≤ -15dB was achieved. Figure 5 As shown.

[0038] In summary, this invention successfully prepared a curved sheet-like terahertz absorbing agent through a self-assembly process and verified its application in couplers. This absorbing material has advantages such as being lightweight, having adjustable absorption properties, and being flexibly integrated for application.

[0039] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A method for preparing a curved sheet-like terahertz absorbing agent, characterized in that, Includes the following steps: Step 1. Dissolve graphene nanosheets (GNS) in deionized water, add graphene dispersant, and stir with a magnetic stirrer to obtain a uniformly dispersed aqueous solution of GNS. Step 2. Add PS balls to an aqueous solution of GNS according to a mass ratio of GNS to polystyrene balls (PS) of (0.1-2):

1. At the same time, add a silane coupling agent to modify the surface of GNS. The organic functional groups of the silane coupling agent combine with the PS balls, and the silanol end of the silane coupling agent forms a covalent bond with the surface of GNS, so that GNS and PS balls are linked. Step 3. Freeze the above-obtained solution at -18℃ to -20℃ for 8h to 10h to form a solid, and freeze-dry for 24h to 30h to obtain a flocculent block. Grind the block to obtain a powder with good flowability, which is the curved sheet terahertz absorbing agent.

2. The method for preparing the curved sheet-like terahertz absorbing agent according to claim 1, characterized in that, In step 1, the dispersant accounts for 1.0 to 1.5 wt% of the graphene nanosheet raw material.

3. The method for preparing the curved sheet-like terahertz absorbing agent according to claim 1, characterized in that, In step 2, the silane coupling agent is added at a mass percentage of 1.0–1.5 wt% of the tablet / sphere solution, and the mixing time after adding the silane coupling agent is 15 min.

4. The method for preparing the curved sheet-like terahertz absorbing agent according to claim 1, characterized in that, In step 2, the diameter of the polystyrene spheres (PS) is 3μm to 10μm.

5. The application of a curved sheet-like terahertz absorbing agent in a coupler, characterized in that, A curved sheet-like terahertz absorbing agent is dispersed in epoxy resin and defoamed to obtain an absorbing slurry. The absorbing slurry is conformally filled into the isolation end of the coupler. After the absorbing slurry is cured, an absorber of the corresponding shape is obtained, realizing the conformal integration of the absorber and the isolation end of the coupler.

6. The application of the curved sheet-like terahertz absorbing agent according to claim 5 in a coupler, characterized in that, The proportion of curved sheet-like terahertz absorbing agent is 5wt% to 20wt%.

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